1. Field of the Invention
The present invention generally relates to a particle analysis and, more particularly, to a particle analyzer for individually separating and then injecting fine particles contained in a suspension or solution. The present invention also relates to a system utilizing the particle analyzer.
2. Description of the Prior Art
As a device designed to individually separate fine particles contained in a suspension and for counting the number of the fine particles, a particle analyzer of a construction shown in FIG. 10 of the accompanying drawings has long been well known in the art.
Referring to FIG. 10 for the discussion of the prior art, the particle analyzer 13 shown therein comprises a constricted passage 1 for the passage of the individual fine particles 6 and having upstream and downstream passages 2 and 3 communicated with the constricted passage 1 and positioned on respective sides of the constricted passage 1 with respect to the direction of flow of the suspension. The particle analyzer 13 also comprises upstream and downstream electrodes 4 and 5 disposed inside the upstream and downstream passages 2 and 3, respectively.
In this construction, when the suspension 30 containing the fine particles 6 is allowed to flow in a direction shown by the arrow A, the fine particles 6 can be individually separated and, therefore, change in impedance between the upstream and downstream electrodes 4 and 5 can be detected. If the frequencY of change in impedance is subsequently counted, the number of the fine particles 6 can be counted.
In other words, according to the prior art, a voltage is monitored when a predetermined electric current is supplied across the electrodes 4 and 5, but an electric current is monitored when a predetermined voltage is applied to the electrodes 4 and 5. Since the impedance across the electrodes 4 and 5 depends on internal conditions of the constricted passage 1 and external conditions in the vicinity of the constricted passage 1, the impedance undergoes change each time the fine particles pass through the constricted passage, which change can be detected in the form of pulses, the number of pulses representing the number of the fine particles having passed through the constricted passage 1.
After the number of the fine particles has been detected in the manner as hereinabove described with tee use of the particle analyzer 13, and when the fine particles contained in the detected suspension are to be injected into suitable containers, the containers are to be arranged immediately beneath the downstream passage 3. While the containers are conveyed successively past a position immediately beneath the downstream passage 3, a predetermined number of the fine particles is injected into each container.
However, the prior art particle analyzer and the prior art system utilizing such particle analyzer have been found having the following problems, particularly when the fine particles are continuously separated and injected with the use of the prior art particle analyzer.
(a) Some of the fine particles separated and injected during the previous cycle tend to be left within the flow system including the constricted passage and the upstream and downstream passages. The fine particles so left within the flow system will be flushed out with the fine particles allowed to flow during the subsequent cycle and, therefore, the fine particles different in number from the required number tends to be injected.
(b) Where the concentration of the fine particles in the suspension is high, the individual separation of the fine particles is difficult to achieve because the fine particles continuously pass through the constricted passage, and, therefore, the number of pulses generated will not accurately coincide with the number of the fine particles counted.
This problem may be substantially alleviated if the suspension is diluted before the detection and counting are performed, however, the time required to perform the detection and the counting will be prolonged and a time-consuming and complicated handling procedures will be required.
(c) Since a predetermined electric current is applied to the electrodes 4 and 5 within the upstream and downstream passages 3 and 4, hydrolysis tends to occur accompanied by the production of hydrogen gas which subsequently forms bubbles. As the bubbles of hydrogen gas pass through the constricted passage 1, and if the bubbles are of a size comparable to the size of the fine particles, the bubbles will be erroneously taken as the fine particles, resulting in a detection error.